Work is primarily concerned with three complex regulatory enzymes: phosphofructokinase, glutamate dehydrogenase and adenylic deaminase. In each case, the relationship between the structure of the enzyme and its catalytic function is being investigated. Techniques used to investigate these enzymes will include stopped flow kinetics, studies of ligand binding by quenching of protein fluorescence, chemical modifications, and x-ray crystallography (of the rat liver glutamate dehydrogenase). Kinetic theory is being developed for hysteretic-allosteric enzymes and computer programs for simulating the time course of enzymatic reactions are being converted into an easily accessible Fortran language.